1. Field of the Invention
The present invention relates to networks, and more particularly to detecting and removing orphaned CLOSE (CLS) primitives in a fibre channel network.
2. Background of the Invention
Fibre channel is a set of American National Standard Institute (ANSI) standards, which provide a serial transmission protocol for storage and network protocols such as HIPPI, SCSI, IP, ATM and others. Fibre channel provides an input/output interface to meet the requirements of both channel and network users.
Fibre channel supports three different topologies: point-to-point, arbitrated loop and fibre channel fabric. The point-to-point topology attaches two devices directly. The arbitrated loop topology attaches devices in a loop. The fibre channel fabric topology attaches host systems directly to a fabric, which are then connected to multiple devices. The fibre channel fabric topology allows several media types to be interconnected.
Fibre channel is a closed system that relies on multiple ports to exchange information on attributes and characteristics to determine if the ports can operate together. If the ports can work together, they define the criteria under which they communicate.
In fibre channel, a path is established between two nodes where the path's primary task is to transport data from one point to another at nigh speed with low latency, performing only simple error detection in hardware.
In a Fibre Channel Arbitrated Loop as defined in the FC-AL standard, the Close (CLS) primitive is transmitted by ports involved in a connection (Loop circuit) to terminate the connection. In most connections, each port involved (i.e., either in the OPEN or OPENED state) should remove the CLS primitive from loop traffic when it is received. If for some reason a port does not remove the CLS primitive (e.g., device failure or extraction from the loop) , the CLS primitive becomes “orphaned” (i.e., unclaimed) and continues to transit the loop indefinitely. The orphaned CLS primitive prevents any subsequent connections from being maintained, destroying the integrity of the loop. There is no FC-AL defined solution for this problem other than a total re-initialization of the loop.
Therefore, there is a need for a method and system that is capable of detecting orphaned CLS primitives and removing them from a loop.